The project consists of three programs that investigate the role of attention in short-term memory and target search in pigeons. By attention, we mean a central cognitive process which determines how an attribute of a stimulus is detected, encoded, stored and retrieved in a memory test. One aspect of attention is that a pigeon processing two stimulus attributes (e.g., line orientation and color) at the same time, processes each less efficiently than it does either alone. This "divided attention" effect has been interpreted as resulting from a division of limited attentional capacity into two parts, resulting in decreased capacity for processing each attribute. When the pigeon attends selectively to one attribute only, performance on that attribute improves, and performance on the "neglected" attribute declines: providing further support for the limited capacity interpretation of divided attention. The first part examines two interpretations of these effects: (a) limited capacity interpretation and (b) peripheral orientation (which asserts that the effects can all be understood by knowing where the pigeon looks). The second part examines the functional significance of selective attention in grain searches under conditions that make the grains difficult to detect. The third part investigates the mechanisms of target detection in a more controlled environment, in which targets and non-target distractors are presented to the pigeons on a touch sensitive monitor to test hypotheses on how attention setting increases search speed. The health significance of this research is that the research will provide an animal model of a sharply-defined cognitive function of wide generality. Since loss of attentional capacity so seriously effects human functioning, the opportunity to mimic and study this cognitive process in non-human's can have practical significance, in that an animal model would allow investigators to impair the cognitive function and to examine programs of rehabilitation.